1. Field of the Invention
The present invention relates to an armature, a wire dot printer head and a wire dot printer.
2. Description of the Prior Arts
There has been known a wire dot printer head wherein an armature with a printing wire connected thereto is pivoted between a printing position and a stand-by position, and when the armature is pivoted to the printing position, a tip of the wire is brought into collision with a printing medium to effect printing. In a certain wire dot printer head of this type, there has been proposed a device wherein a magnetic flux is produced by a coil around the armature to be pivoted for forming a magnetic circuit that causes the armature to be attracted from a stand-by position to a printing position to effect printing.
It has been known that, in the wire dot printer head described above, an eddy current loss is caused by a ripple (change) in a flux passing through the armature. In order to restrain the eddy current loss to prevent the deterioration in magnetic characteristic, there has been proposed a technique for forming an armature by laminating plural thin plate-like members (see Japanese Unexamined Patent Publication No. 11336/1990). The patent document 1 discloses that plural plate-like members are coupled together with an engagement to integrally form an armature. The space between these plural plate-like members is spot-welded to be joined together.
However, the armature disclosed in the Japanese Unexamined Patent Publication No. 11336/1990 is formed such that plural plate-like members are coupled together with an engagement, so that a gap is present between the adjacent plate-like members, thereby deteriorating adhesion. Further, it is difficult to decrease a dimensional tolerance at the engagement section, so that the adhesion goes on deteriorating. This reduces magnetic characteristic of the magnetic circuit, whereby the stabilized pivotal movement of the armature cannot be realized, and further, magnetic characteristic required for high-speed printing cannot be obtained. As a result, it is impossible to execute high-speed printing. In particular, the armature is required to be pivoted 2500 times per second between the printing position and the stand-by position with a recent increased printing speed. Therefore, the deterioration in the magnetic characteristic becomes an important problem.